Magnetic inductor switch



Nov. 20, 1962 A. E. PRINCE 3,065,318

MAGNETIC INDUCTORY SWITCH Filed April 24, 1961 flPTA/UP ENNIS PPM/C E I N V E NTOR United States Patent 7 3,065,318 MAGNETIC INDUCTOR SWITCH Arthur Ennis Prince, Boonton Township, Morris County, N.J.-, assignor to Otis Elevator Company, New York, N.Y., a corporation of New Jersey Filed Apr. 24, 1961, Ser. No. 105,118 22 Claims. (Cl. 200-87) The present invention relates to inductor switches and like magnetically operated devices, which may find use in connection with the electrical control system of elevators, and other installations, such as power presses, machine tools and the like.

Inductor or magnetic switches were heretofore known, which employ a neutralizing vane adapted to be interposed between the like poles of a movable and a stationary magnet, of which one is a horizontally extending bar magnet and the other is a horseshoe magnet, where by like poles of said two magnets are located in spaced alignment to and opposite each other, so that these magnetic poles may be magnetically insulated from one another. In such case the magnetic lines of force of the horseshoe magnet pass through said vane, draw the movable magnet toward the latter for operating an electric circuit.

Other known switches or relays of this type propose a two-part armature, permitting the two parts to move in opposite directions and in juxtaposition to the poles of a magnet.

In this case the armature is released by causing either a magnetic member to move in close proximity to the pair of poles, so as to reduce the attraction between the other pair of poles and the armature or to enter a gap formed by the divided pole pieces.

These and other known magnetically or electromagnetically operated switching devices have, however, considerable disadvantages in that they are inconvenient for access and installation, are cumbrous in assembly, take up a rather large space and are consequently complex and unsteady and insufiiciently sensitive in operation.

The present invention overcomes these and other inefiiciencies and drawbacks of the prior art and has as one of its primary objects to provide means contributing to a highly eiiicacious, compact and highly sensitive inductor switch structure, whose operable parts are completely enclosed in a casing, are consequently kept free from dust or atmospheric influences and do not require any spring or resilient force actuation and like extraneous agency.

It is another object of the invention to provide means ensuring automatic, reliable and accurate control operation of the magnetic switch regardless of its upright or horizontal position with respect to a base on which the switch structure is to be mounted, thereby oifering great flexibility in accommodating the switch assembly.

Another object of the invention resides in the provision of means rendering the possibility of arranging stationary and movable magnetic parts of the switch structure at right angles to each other in a hermetically sealed casing, if desired and further of influencing these magnetic parts by means of a vane which is adapted to be located substantially parallel and in the proximity to said magnetic parts during the course of performing operational switching steps.

A further object of the present invention is to provide means leading to a highly economical and inexpensive inductor switch structure which is light in weight and whose operation may be improved by incorporating therein means for regulating or adjusting the density of the lines of magnetic force at predetermined locations of the structure.

Yet another object of the invention resides in the pro- "Ice vision of means conducive to a high-speed and sturdy magnet inductor switch device, which is substantially devoid of wear and tear despite high switching frequencies, is not disturbed by gravitational or jolting forces, is not dependent for operation on a path of the vane through a relatively narrow slot or gap with small tolerances and relies on commercially available, angular-shaped vane profiles without requiring any reinforcement therefor.

Still a further object of the invention is to provide means rendering the possibility of altering position, thickness and length of the vane member in accordance with the power of the magnetic elements of the switch device without changing the shape of the casing in which the magnetic elements and switch blades or like operable elements are accommodated.

These and other objects of the invention will ensue from the following description and claims, as well as from the drawing attached thereto in which:

FIGURE 1 is a top plan view of an inductor switch device embodying the invention, shown in horizontal position and looking into the interior of its casing and onto a magnetizable vane member;

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1, as seen in the direction of the arrows; and

FIGURE 3 is a sectional view taken along line 33 of FIGURE 1 as seen in the direction of the arrows.

Referring now more particularly to the attached drawing there is disclosed a magnetic inductor switch 10 which comprises a casing 11 having upright walls 12 with reinforced corner sections 13 which are provided with threaded bores 14 for receiving screw bolts adapted to attach a closure or cover 11a to the flat top 15 of the casing body. The body of the casing, as well as the cover are made from non-magnetic material, such as plastic, plastic composition, brass, aluminum and the like. Casing 11 and its cover are provided with an extension part 16 defining with the remainder of casing 11 a recess or indentation 16a for a purpose later set forth. Extension part 16 of the casing is integral with the latter and contains a magnetic element 20 preferably made of ceramic magnetic material. This magnetic element 20 may be of elongated rectangular shape, as shown and is adapted to co-operate with another rectangular ceramic magnetic element 21.

Magnet elements 20, 21 are normally spaced a predetermined distance from each other. Their spacing may, however, be regulated, for example, by means of an adjustment screw 17 extending through a threaded wall opening 19 into the interior of the casing. One end of screw 17 is provided with a clamp 18 for firmly gripping one end of lengthy magnet element 20 so that the latter may perform a sliding movement or displacement relative to element 21, if desired. To this end, element 20 is seated and guided in suitable rails 22.

If magnetic element 20 has, for example, a north pole at one end 23 and a south pole at an opposite end 24,

. then magnetic element 2.1 is provided with a frontal north pole layer 25 and with a rearward south pole layer 26, so that magnetic element 20 with north pole at end 23 extends at substantially right angles to extremity 27 of element 21 and preferably in the same plane as depicted in FIGURE 1.

Magnetic pole layer 26 carries an iron strip or shim element :29 of magnetizable material, which may be sandwiched between layer 26 and surface of support 28, whereby increased magnetic flux on frontal magnetic layer 25 will be established. Support element 28 is provided with a ing 30 through which extends a pivot or like pin 31 which lug is supported in bracket 32 ailixed at 32a by a screw or the like to a supporting or partition plate 42.

In order to retain magnet 21 in laterally adjusted position with respect to support or holder element 28,

centering lugs 33 depend from the latter in downward and lateral direction near the other extremity 34 of magnet element 21, as shown. The interconnection between magnet 21, carrier or holder 28 and strip 29 forming together unit 35, may be effectuated, as by gluing or other fastening means (rivets, screws or bolts), so that this composite unit 35 may be swung about pivot pin 31 to and from one actuated to another inclined extreme switching position, as indicated by dot and dash lines at 35a.

Top 28a of holder 28 carries at 63a two switch blades 36 provided with contact pieces 37, 38 adapted to make and break contact with corresponding stationary contact pieces 40', 40a which are disposed on brackets 39, 39a mounted by means of terminal posts or screws 41 on the inner surface of partition wall 42 of casing 11, as depicted in FIGURE 1.

Through this wall 42 extends further an abutment screw 43 for limiting the swingable movement of unit 35 to position 35a by means of abutment pad 35b in one extreme switching position about pivot pin 31.

Wall 42 is slidably inserted in guide grooves 44 and is normally retained therein in position by any suitable spring means 44a. By slidably moving unit 35 together with partition wall 42 out of guide grooves 44 attachment of wires or like conductors (not shown) to terminal posts 41 may be facilitated, whereby such conductors may be introduced into the interior of the casings through opening or socket 45.

It is well understood that this latter opening 45, as well as opening 19 for adjustment screw 17-18 may be sealed in any appropriate and known manner, in order to obtain, if desired, an inductor switch casing, which is hermetically closed. 7

The operation of the inductor device is as follows:

As the stationary and movable magnets 20, 21 are enclosed in the casing 11 a preformed or angular-profiled vane member 46 may be arranged, so as to influence the magnetic flux (repulsion) between the like poles of said magnets 20, 21 when the vane member during relative movement of the casing to the vane member arrives at or is located in the proximity of the magnetic inductor device within recess 16a.

In such case leg 47 of the vane member extends substantially in parallel and spaced relation to and lengthwise of movable magnet 21, whereas leg 48 of the vane member will be located substantially parallel to and spaced along the extent of magnet '20 (which may be stationary or displaceable relative to said leg 48 and to magnet 21).

Dimensions of legs 47 and 48 of vane member 46 are so selected that, on the one hand, sufiicient tolerance will be had to'ensure relative movement of the casing 11 to the vane member 46 and, on the other hand, to adequately exert influence of the magnetic vane member on the magnet array within casing 11; 7

As magnet 20 normally exerts a repulsing action on magnet 21 and thus on unit 35, the latter is swung about pivot pin '31 and assumes one extreme position 35a in which disengagement of contacts 37 from stationary contacts 40 is elfectuated.

When the aforesaid vane member 46 is located in or passes through recess 16a most of the magnetic lines of force from magnet 20 will be deviated toward vane part or leg 48 to an extent that the repulsion force between magnet pole 23 and magnet layer 25 at extremity 27 of magnet 21 is substantially reduced, leaving a re pulsion force which is overcome by the simultaneously established attraction force between magnetic layer 25 and vane part or leg 47 of the vane member 46, which attraction force is of sufficient magnitude to bring about a switching operation ofcontacts 38 with stationary contacts 40 in another extreme position of unit 35. "It

,is to be noted that "according to the invention the magneti'c repulsion force in released condition of the magnetic switch (without vane) is substantially equal to the attraction fiorce in operated condition of the switch (with vane in place), so that pressures exerted on the above contacts are always substantially of the same value.

As shown in the drawing L-shaped casing 11 is normally disposed in a horizontal plane in which nov gravitational or other extraneous forces act on unit carrying magnet 21, so that repeated switching operations of high speed and frequency may be had without disturbances.

It is also apparent, that when vane member 46- is removed from recess 1641, the attraction between magnet 21 and vane part 47 ceases and at the same time the normal repulsion between magnets 20, 21 is reestablished. This results in a fast action at increased sensitivity, which may be utilized with great advantage in double switching operations (actuation of contacts 38, and 37, 40a). Adjustment screw 43 is adapted to abut against resilient pad 35b during return swing of unit 35 and may be also employed to regulate the'relative positioning of the aforesaid contacts.

In the event that the inductor switch structure is to be used in uprightcondition (instead of horizontal condition) provision is made to adjust magnet 20 in regard to its position to magnet 21 by means of the aforesaid set screw 17 (see arrows A), whereby magnet 20 may be slidably moved closer to magnetic pole layer 25 of magnet 21 from without casing 11, thereby to compensate for the weight of unit 35, which is minimized by the employment of ceramic magnet material for the magnets and of plastic material for the support 28,

If desired, magnet 20 may not only be adjusted in lengthwise direction thereof, but also in lateral direction to its longitudinal axis so that to a certain degree the magnetic field between magnet 20 and vane member leg 48 and flux leakage therebetween may be controlled by suitable adjustment means and shims (not shown) ,so that magnet 20' may be displaced relative to the adjacent wall of casing 11 (see arrows B).

It is preferred that the outermost ends of the legs 47, 48 of the vane member project to a certain amount beyond the corresponding end or ends of the magnets, so as to reduce leakage of the magnetic flux at the outer magnet ends. V

The operation of the present magnetic switch is based on a compound action which consists of a shunting action between leg iOI' vane part 48'and bias magnet 20 on the one hand, and an action of attraction between leg or vane part 47 with respect to main or movable magnet 21. Since the vane member 46 is not' interposed between magnets 20, 21, it leaves more latitude for adjustment purposes and does not move through an air gap with required large running clearance betweenthese magnets as in known inductor switches, the variable air gap 16b of the proximity switch according to the invention may be kept very small and consequently magnet bodies of-reduced size and force and of considerably small cost may now be utilized, as the aforesaid known switch structures require 'large and strong magnets, which necessitate an air gap of considerable width through which thervane passes, to thereby completely neutralize the bias magnet flux in a series circuit, in which the magnetic field of force is established solely via the vane with the main or pivotally supported magnet,

7 According to the invention the reluctance of magnet 21 in regard to vane part 47 can 'be increased and a of the'repulsion force between relative movable and displaceable magnets 20', 21). Thus, less contact bounce at a reducedcontact' impact and'less noise from switching operations will be had than it, is possible with other inductor switches now on the market. Besides this, the life of the switching contacts will be markedly increased.

The new proximity switch affords an extremely small differential between the relative location (in the direction of motion) of the vane and of the switching magnets to effect operation and release of the switching contacts. This differential constitutes a measure of the degree of sensitivity and dependability of the magnetic switch, which is considerably enhanced and was not readily obtainable in known magnetic switches, which require a far greater vane motion Within a relatively large air gap intermediate their magnets.

According to the invention it is possible without any difiiculty and without changes of the size and strength of the force of the magnets to vary this differential for example, by decreasing the switch sensitivity for a delayed switching action without affecting the vane clearance through adjusting the relative location of the magnets with respect to each other, as pointed out hereinabove (see arrows A and B).

In order to avoid abutment of face 25 of magnet 21 against the adjacent casing Wall, non-magnetic piece or plastic pad 5% may be provided on said wall for holding unit 35 in substantially parallel planar position to leg 47 when the vane member moves relative to the casing within space 16a.

Dimensions of the non-magnetic case 11 and its weight together with that of ceramic magnets 20, 21 result in a very light and compact and adequately regulatable and dependable proximity switch structure, which is completely devoid of any spring or similar force-exerting elements, may be easily installed in horizontal or vertical operable position and can be utilized in a great variety of applications on elevator systems, power presses and in fabricating plants, whereby one of the magnets may be sationary (or displaceable, if desired) while the other magnet is pivotally disposed for effectuating switching and like operations. Servicing of the novel magnet actuator array becomes negligible, as corrosion and other undesirable influences are completely avoided due to the use of a sealed casing, in which all vital parts are enclosed.

It might not always be necessary to use a pivotable support 28, 30 for the movable magnet component 21 and to directly journal such magnet component 21 relative to the other or stationary magnet component 20 and to mount the switching blades 36, 37, 38 or the like directly on movable magnet 21.

It will be recognized, that while the invention has been disclosed in connection with certain specific details of a preferred embodiment thereof which has given satisfactory operating results, such details are not intended to be limitative of the invention as set forth in the annexed claims.

It can thus be seen that there has been provided in accordance with this invention a magnetic inductor switch comprising a first permanent magnet, a second permanent magnet, said magnets being disposed in substantially the same plane and with the same poles spaced from and at right angles to each other, first means pivotally mounting one of said magnets with respect to the other magnet, second means for regulating the distance of said second magnet to said first magnet, and a vane element having legs arranged at right angles to each other and respectively extending substantially parallel to said magnets and at a preselected distance from the latter, so that one of said legs exerts a shunting action on said second magnet and reduces the repulsion force established between said first and second magnets, while the other leg decreases the reluctance to and attracts said first magnet to a sutficient extent, to overi come the reduced repulsion force and to bring about pivotal movement of said first magnet for switching purposes.

As changes can be made in the above described con- 6 struction and many apparently different embodiments of this invention can be made without departing from the scope thereof, it is intended that all matter con tained in the above description or shown on the accompanying drawing be interpreted as illustrative only and not in a limiting sense.

What is claimed is:

1. An inductor switch device comprising a casing, a first magnet having one elongated face, a lengthy second magnet having opposite ends, both said magnets being enclosed in said casing and extending in substantially the same plane and at right angles to each other, so that said face of said first magnet confronts one of the ends of said second magnet, said one end of said second magnet being spaced from said one face of said first magnet at one extremity thereof and having the same polarity thereby to repulse said first magnet to assume a first position, an element of non-magnetic material pivotally journaled in said casing and supporting said first magnet, whereby the latter may be pivoted to said first switching position, a vane member without said casing and disposed for movement relative to said casing and including one leg extending in spaced and substantially parallel opposed relation to said one face of said first magnet, a further member arranged to extend substantially parallel to and spaced from said second magnet sufficient to deviate magnetic flux from said one end of said second magnet via said further member to the opposed end of the second magnet, so that said one leg of said vane member exerts sufiicient attraction on said first magnet to pivotally move the latter from said first switchingto a second switching position, and respective co-operable contact means located in said casing and on said element for operating electric circuit means due to movements of said first magnet relative to said second magnet and from said first to said second position, respectively.

2. A device according to claim 1, said vane member being profiled in cross-section, said further member forming another leg of said vane member and extending at right angles to said one leg.

3. A device according to claim 1, said first magnet having another elongated face coextensive with and located rearwardly of said one elongated face, and a plate of magnetizable material sandwiched between said one element and said other elongated face.

4. A device according to claim 1, said element being provided with a lug having an opening and located adjacent an extremity of said first magnet which is opposite to said one extremity of the latter, and a pivot pin supported in said casing and engaging said lug in said opening to ensure pivotal movement of said first magnet to said switching positions.

5. A device according to claim 1, including means on said supporting element for centering said first magnet to said supporting element.

6. An inductor switch device comprising a casing, a first magnet divided into two opposite lengthy pole faces, a second magnet having opposite pole-forming ends, both said magnets being accommodated within said casing and extending at right angles to each other, so that one of said pole forming faces of said first magnet confronts one of the pole forming ends of said second magnet, said one end of said second magnet being spaced a predetermined distance from said one face of said first magnet and having the same polarity as that of Said one face of said first magnet thereby to produce a repulsion force between both said magnets, an element supporting said first magnet and made of non-magnetic material pivotally journaled in said casing, whereby said first magnet is pivotally movable from a first operable position to a second operable position, and an angularshaped vane member disposed for movement relative to and without said casing and including one leg extending in spaced and substantially parallel opposed relation to one face of said first" magnet and another I leg "arranged to A extend substantially parallel to i and spaced from said second mag net suiiicient to deviaterhag netic flux from said one end ofsaid secondmagnet'via'said otherleg to the oppositeend offthe'fsecond'magnet, so that said one leg of said vane mern-ber' exerts' attraction onsaid first-magnet suflicient to pivotally m ove' the latter from" said first tos aid secon d operable position. 7. A device according toclair n 6, lthelegs of said vane member extending at right angles to each other with the intersectionof said legs located about level with the one end or said second magnet. I 8. A device 1 accordingto arm 6,'said one face of said first magnet being eoextensivef'with the" other face of said first magnet and being located forwardly of the latter face. 7 p 7 9. A device-"according tlo claime, said supporting element being provided with a pivot pin iabout which said supporting element together with said first magnet may swingably move from and tosaid operable'positions, respectively. i

10. A deviceaccordingto claim 6, including lug means depending from said supporting element for facilitating centering of said first magnet relative to said supporting element. 7

11. A device acc ording to claim 6, including a shirn plate of magnetizable material interposed between the other face of said first magnet and the adjacent supporting element. s v

12. A device according to claim 6, including a partition mounting said supporting element and said first magnet and slidably engaged within recesses provided in opposite walls of said casing. I v

13. A magnetic inductor device comprising a casing, a first magnet composed of two successive lengthy-faces with opposed poles, a second magnet having oppositepoleforming ends, both said magnets being located within said casing and extending'inthe same plane at right angles to each other, so that one of the said pole-forming faces of said first magnet confronts one of the'pole-forming ends of said second magnet, said one endof said second magnet being spaced a predetermined distance from said one face of said first magnet and being of the same polarity as that of said one face of said first magnet, thereby to produce a repulsion force between both said magnets, said first magnet being pivotally journaled in said casing, whereby said first magnetmay pivotally move from a first position to a second position, a vane member of magnetic material disposed for movement relative to and Without said casing,said vane member extending at least partly in spaced and substantially parallel A relation to said one face of said first magnet, and a further member of magnetic'material arranged to extend substantially lengthwise of and adjacent said'second magnet thereby to divert magnetic flux from said one end of said' second magnet via said'further m'em-ber to the opposite end of the second magnet, so that between saidvane member end of 'said second magnetterminates a predetermined distancefrom' one'extremity of the frontal race of said first magnet, both said one end ofsaidscoridmagnet and's'aid frontal face of said first magnet being of the same polarity, first means pivotally supporting said first magnetfor movementrelative to said second magnet, second means for displacing said second magnet with said oneendtowa'rd and awayfrom said extremity of said first inagnen thi r d means operatively connected to said first magnet for performing switching operations, and an angular shaped'vane member having respective legs spaced a predetermined distance from and' parallel to said magnets, said legs extending wtih their respective ends beyond the outermost ends of said magnets.

17. An inductor switching device comprising a first permanentmagnet, asecond permanent magnet, said magnetsbeing disposed substantially the same plane and with the like poles spaced from and at right angles to each other, first nieans'pivotally mounting one of said magnets with respect to; the 'oth erirna gnet, second means for regulating the distance of said second magnet to said first magnet, and a magnetic "vane element having legs arranged at right angles to each'ot her and respectively extending substantialiyparallelfto said magnets and at a preselected distance from the latter, so that one of said legs exerts a shunting action on said second magnet and 7 reduces therepulsion force established between said first and said first magnet sufficient magnetic attraction is ex- 7 justably displacing the latter" relative to said first magnet.

16, An indutor'switch device comprising a first permanent magnet having afrontalface and a rearward'face, a

second permanent magnet' having twooppositeends, said magnets' being" spaced 'f'ro'm"ea'ch other and "extending at an angle to each other in a single plane, so that one and second magnetsQwhile the other leg decreases the reluctance to and attracts said first magnet to a sufiicient extent, to overcome the reduced repulsion force and to bring about pivotalmo'vement of said first magnet for switching purposes, 7 I i 18. A device according to claim 17, including a casing of non-magnetic material, in which said magnets are mounted, and a cover on said casingfor sealing both said magnets therein, said casing being of L-shaped configuration.

19. A switch device comprising a first pe rmanent'rnagnet having opposite pole faces, a second permanent mag-' net having opposed pole ends, said magnets being disposed in substantially the same plane with one pole face of said first magnet at one extremity thereof confronting'the like pole end of said second magnet, said magnets being spaced a predetermined distance from and atright angles to each other sufficient to establish a magnetic repulsion between said magnets, pivot means *near the other extremity of the first magnet mountingthe latter for movement relative to the second magnet, respective magnetizable means adapted to be placed in-spaced, co-operative tandsubstantially parallel relation with said magnets, so

that said magnetic repulsion between the like poles of both said first and second'magnetsis minimizedby the placement of one of said magnetizable means adjacent said second magnet and attraction is effectuated on said first magnet by the other magnetizable means, thereby to pivotally displace said first magnet for switching operation, the magnetic repulsion force in released condition of both said magnets and upon removal of said magnetizable means being substantially equal to the magnetic attraction force in operated condition of said magnets and upon placement of said magnetizable' means adjacent said magnets, whereby about thesarne pressure is exerted on contacts eifectuating said switching operation, and means of magnetizable material located on the. other pole face of 'said first magnet and remote from said one poleface of said first magnet'thereby to increase the magnetic field on the latter pole face.

20. A switch device'c'orriprising a first magnet, a second magnet, said magnets being disposed in substantially the same plane with one pole of said first rria'gnet c onfronting'the like pole of'saidsec'ond magnet, said magnets being spaced a predetermined distance from and extending with their like poles at right angles to each other sufiicient to establish' normally a magnetic repulsion between said like poles of said magnets, pivot means mounting one l of said magnets for movement relative to the other magnet, and respective means of magnetic material co-ordinated to said magnets and adapted to be placed in spaced and substantially parallel relation to said magnets without the confines of the latter, so that said repulsion between said like poles of said first and second magnets is minimized by the substantially parallel placement of one of said means adjacent said other magnet, while attraction by the other means is efiectuated on the movably mounted magnet to thereby displace the latter for switching purposes.

21. A vane operated magnetic inductor switch device comprising a substantially L-shaped casing of non-magnetic material, a first magnet having opposite pole faces, a second magnet having opposite pole ends, support means for said first magnet arranged within said casing for displacing said first magnet relative to said second magnet within said casing, first contact means arranged on said support means in said casing for a movement commensurate with the displacement of said first magnet, second contact means held stationary in said casing and located in the path of said first contact means and for co-operation therewith, said magnets extending substantially at right angles to each other within said L-shaped casing, like poles of one of said pole faces and of one of said pole ends being spaced a distance from each other sufficiently to normally establish a magnetic repulsion between said first and second magnets so that said first contact means normally assumes a first switching position with respect to said second cont-act means, while upon reduction of said repulsion by the agency of a vane of magnetizable material, said first magnet is displaceable so that said first contact means assumes a second switching position with respect to said second contact means, and a mounting plate retained in said casing and for removal therefrom and carrying said support means, said first magnet and further said first and econd contact means.

22. A vane operated inductor switch device comprising a closable casing of non-magnetic material, two elongated magnets arranged at substantially right angles to each other in said casing, switch blade means equipped with contact points, two sets of stationary contact points arranged in said casing and located for coaction with said contact points of said switch blade means, respectively, support means pivotally journaled in said casing, one of said magnets being carried by said support means for pivotal movement of said one magnet relative to the other magnet, said switch blade means being mounted on said support means and being adapted to move said switch blade contact points in contact with one set of said sationary contact points in one position of said one magnet and in contact with the other set of said stationary contact points in another position of said one magnet, and a partition retained in said casing and for removal therefrom, said partition carrying said support means with said one magnet and said switch blade means and further mounting said sets of stationary contact points, said casing including walls extending at substantially right angles to each other and lengthwise of said magnets, respectively, and in the proximity of the latter to form a recess for the vane.

References Cited in the file of this patent UNITED STATES PATENTS 1,639,190 Knutsen Aug. 16, 1927 2,189,597 Wells Feb. 6, 1940 2,235,104 Greenly Mar. 18, 1941 2,598,214 Borden May 27, 1952 2,843,697 Beck July 15, 1958 

